Alcohols, including higher molecular weight alcohols having from three to six carbon atoms, can be produced industrially by a variety of processes. Some processes include the production of such alcohols by fermentation, e.g., by microorganisms that make the alcohols through metabolic processes. A challenge for the successful industrial production of such alcohols, in addition to producing them in commercially relevant quantities, is the recovery and purification of the alcohols from solutions in which the alcohols are very dilute, such as fermentation broths. For example, butanol produced by fermentation can be in solutions at concentrations on the order of just a few weight percent (e.g., from about 0.5 wt. % to about 10 wt. %).
Methods for the recovery of alcohols from fermentation broths have been described. For example, U.S. Pat. No. 8,101,808 and United States Patent Publication No. 20110124068 disclose exemplary processes for recovery of alcohols from fermentation broths.
Alcohols can be used in a variety of practical applications. For example, some alcohols such as ethanol and butanol can be used as biofuels, typically as an additive in combination with other fuels (e.g., gasoline). There are other uses of industrial alcohols as well, including use as solvents, or as precursors for the production of higher molecular weight compounds. However, different applications for the use of such alcohols have different purity requirements for the alcohol product(s). A variety of factors can affect the utility of any given recovery and purification process, including its recovery efficiency, as well as capital, operating and maintenance costs. Accordingly, there is a need for processes for the recovery and purification of such alcohols that are cost-effective and efficient, and that allow for the production of alcohols at levels of purity that are appropriate for an intended application.